Fine Gael TD for Westmeath Paul McGrath will stand down at the next general election, it emerged tonight.
The unexpected decision will come as a blow to his party's hopes to retain the seat and secure enough TDs to form an alternative coalition with Labour.
In the 2004 review of constituency boundaries, part of Mr McGrath's Mullingar base was taken in by new constituency, Meath West.
However Fine Gael leader Enda Kenny said tonight that he believed Mr McGrath would still have been comfortably re-elected.
Paying tribute to his deputy finance spokesman, Mr Kenny said he was informed of the decision earlier this week.
He described Mr McGrath, who was first elected in 1989, as a tireless worker for his constituency and the party.
He added: "Paul's use of Parliamentary Questions was an example to any deputy on how to extract information of importance and relevance to the electorate. He publicised many important issues in this fashion over the years.
"I look forward to working with him for the duration of this Dail as we build up to the forthcoming general election - an election where indications on the ground suggest that Paul would have been comfortably re-elected."